This invention relates to a supported catalyst component, to a process for preparing such a supported catalyst component, to an olefin polymerization supported catalyst composition, and to an olefin polymerization process using such a supported catalyst.
Supported catalysts of the so-called Ziegler or Ziegler-Natta type can be used in the polymerization of olefins in high pressure, solution, gas phase, and suspension or slurry processes. In typical slurry and gas phase processes the polymeric products are obtained as solid particles. In such processes small polymer particles or a large particle size distribution should be avoided, as buildup of small particles can cause entrainment problems in the reactor, valves or transfer lines. Further, low polymer bulk densities cause difficulties in operations where gravity feed is required, such as transfer to extruders, and increase the volume required for powder storage or shipping containers.
U.S. Pat. No. 4,526,943 discloses an olefin polymerization catalyst prepared by the reaction of a hydrocarbon soluble organomagnesium compound with a trialkylaluminum and an aliphatic alcohol to generate a soluble magnesium alkoxide precursor to which is added a transition metal compound, typically a titanium compound. A supported catalyst is then prepared by precipitation of a magnesium halide using a reducing metal halide, such as ethylaluminum dichloride. These supported catalysts can achieve high efficiencies on a transition metal basis and yield polymer powder of the desired particle size and bulk density, yet the high levels of alkylaluminum halide required to precipitate the catalyst results in relatively high levels of aluminum and chloride in the final polymer. In addition, alcohol is generated as a by-product of typical catalyst deactivation procedures, which alcohol is difficult to remove from solvent recycle streams and requires expensive separation and purification procedures.
Other efforts to control catalyst efficiencies and polymer morphology for Ziegler-type catalysts focused on supporting typical Ziegler catalysts containing a transition metal compound and a magnesium halide on metal oxides such as silica and alumina or polymer supports.
U.S. Pat. No. 4,639,430 describes a catalyst support consisting essentially of a mixture of silica and a magnesium chloride, said support having a porous texture and containing less than 100 micromoles of hydroxyl groups per gram of support, as well as olefin polymerization catalysts consisting essentially of such supports and at least one active component of a group IV, V or VI halide.
U.S. Pat. No. 4,405,495 describes the pretreatment of a particulate silica support having a particle size distribution of from 2 to 80 microns and an average particle size of from 20 to 50 microns with a precursor compound containing magnesium, titanium, halo, electron donor and optionally a hydrocarbyloxy or carboxylate group. The support can be pretreated with an aluminum alkyl. The precursor is dissolved in the electron donor and impregnated on the silica support.
U.S. Pat. No. 4,301,029 describes the preparation of a catalyst component by reacting a solid inorganic support with a magnesium hydrocarbyl compound, a halogenating agent, a Lewis base compound and titanium tetrachloride. Preferably after each step the product is washed and separated.
U.S. Pat. No. 4,324,691 describes the preparation of a catalyst component by reacting a particulate support material, preferably first with an aluminum compound, then with an organomagnesium compound, a transition metal compound, and a pacifying agent such as hydrogen chloride, and optionally an organometallic compound, a halogenating agent or a Lewis base.
U.S. Pat. No. 4,481,301 discloses the preparation of a supported olefin polymerization catalyst by treating a solid porous carrier in a liquid medium with an organomagnesium compound to react with the OH groups on the carrier, evaporating said liquid medium to precipitate magnesium onto the carrier and recovering a supported magnesium composition in the form of a dry, free-flowing powder. The powder is reacted with a tetravalent titanium compound in a liquid medium.
U.S. Pat. No. 3,787,384 discloses the preparation of supported catalyst components by impregnating a metal oxide such as silica or alumina, with an organometallic magnesium compound, selected in particular from magnesium alkyl and Grignard compounds, and reacting the obtained product with a titanium halide compound.
U.S. Pat. No. 4,263,168 describes catalyst components for the polymerization of propylene and other alpha-olefins, obtained by reacting a metal oxide, such as silica or alumina, containing hydroxyls on the surface, with an organometallic magnesium compound of the formula MgR.sub.2-x X.sub.x (where R is a hydrocarbon radical; X is halogen; x is a number from 0.5 to 1.5), and subsequent reaction with an electron-donor compound and titanium tetrachloride. As a variant, the metal oxide, either before or after the reaction with the organometallic magnesium compound, can be reacted with a halogenating agent which will supply at least one halogen per hydroxyl group.
U.S. Pat. No. 5,139,985 describes catalyst components obtained by supporting a magnesium dihalide or a magnesium compound which can then be transformed to dihalide on a porous polymer support, and reacting this solid with a titanium halide or titanium halogen alcoholate, optionally in the presence of an electron-donor compound.
U.S. Pat. No. 5,064,799 describes catalyst components obtained from the reaction of a tetravalent titanium halide and an electron-donor compound with a solid obtained by reacting a metal oxide containing surface hydroxyl groups (such as silica or alumina) with an organometallic magnesium compound of the formula MgR.sub.2-x X.sub.x, where R is a hydrocarbon radical, X is a halogen or an OR or COX' radical (where X' is halogen) and x is a number from 0.5 to 1.5, used in amounts such as not to cause reduction of titanium during the subsequent reaction of the solid with the titanium halide.
U.S. Pat. No. 5,227,439 describes a solid catalyst component obtained by preparing a solution of magnesium chloride in ethanol, impregnating activated silica particles with this solution, adding to this suspension a titanium compound and silicon halide, eliminating the ethanol to recover a solid, reacting the solid with alkyl aluminum chloride, and recovering the solid catalyst component.
U.S. Pat. No. 5,244,854 describes a catalyst component for the polymerization of olefins obtained by reacting a tetravalent titanium halide or titanium halogen alcoholate and an electron donor compound with a solid comprising a porous metal oxide containing surface hydroxyl groups, on which is supported a magnesium dihalide or a magnesium compound which can be converted to a magnesium dihalide.
U.S. Pat. No. 5,278,117 describes a supported Ziegler-Natta catalyst consisting of a cocatalyst and a solid catalyst component obtained by impregnating a granular porous solid support with a solution of magnesium chloride and a titanium tetraalcoholate in a liquid aliphatic hydrocarbon, evaporation of the solvent, impregnation with a solution of magnesium chloride in an aliphatic ester, evaporation of the solvent, and activation with an alkyl aluminum chloride.
It is desired to provide a supported catalyst component and a supported catalyst which can be used in olefin polymerization processes, in particular in slurry or gas phase type processes, to give olefin polymers with desired morphology and bulk density at high catalyst efficiencies. It would further be desirable to provide a supported catalyst component which is storage stable.